1. Field of the Invention
The present invention relates to a diaphragm for a flat-type acoustic transducer, which is to be used in a flat-type acoustic transducer such as a flat-type speaker, a flat-type microphone, a flat-type speaker that is usable as a microphone, or the like, and relates to a flat-type acoustic transducer that uses this diaphragm for a flat-type acoustic transducer.
2. Description of the Related Art
Examples of flat-type acoustic transducers include a dynamic flat-type speaker disclosed in Japanese Patent No. 3,159,714.
In this flat-type speaker, a plurality of permanent magnets are disposed neighboring each other and separated by a predetermined spacing such that polarities thereof intersectingly oppose one another. A diaphragm is provided facing the permanent magnets and disposed at a predetermined separation therefrom.
Coils are formed at the diaphragm in correspondence to the respective permanent magnets. The coils are formed in a coil shape.
When electric current is passed through the coils, a force acts in a direction orthogonal to a membrane surface of the diaphragm. The diaphragm is displaced in the direction orthogonal to the membrane surface.
Consequently, by passing electrical signals representing sounds that are desired to be emitted through the coils, the diaphragm is caused to oscillate in accordance with the electrical signals, and acoustic signals are emitted.
In the dynamic flat-type Speaker disclosed in Japanese Patent No. 3,159,714 and in other conventional dynamic flat-type speakers, because the conductors are formed as coils formed in coil shapes, a width of each conductor is extremely narrow.
Further, in these flat speakers, permanent magnets are provided for each of the conductors formed in coil shapes.
Such conductors may be formed by laminating, vapor-depositing, adhering or the like a metallic film of copper, aluminium or the like onto a diaphragm fabricated of synthetic resin. This metallic film can then be structured by etching.
In a case where the plurality of coil-shaped coils is arranged at only one side of the diaphragm, and this plurality of coil-shaped coils is connected in series, in order to connect an end portion of an inner side of one coil with an end portion of an outer side of another coil, it is necessary to dispose conductive wiring for connection at a side of the diaphragm opposite to the side thereof at which the coils are formed, and it is necessary to connect the coils with this conductive wiring for connection, via through-holes.
When a plurality of coil-shaped coils are connected in series, through-holes are necessary for all the coils (for all the magnets), and a plurality of the through-holes is formed in the diaphragm. Consequently, when a connection failure at a through-hole portion occurs, an examination for investigating at which portion the connection failure has occurred is complex. Thus, there is a problem in that dealing with cases in which connection faults have occurred is complex.
Furthermore, even if the coil-shaped coils are disposed at both sides of the diaphragm, the coils at a front surface side and the coils at a rear surface side have to be connected via through-holes, and the same problem arises.
Therefore, there is a problem in that fabrication of diaphragms for flat-type speakers is more difficult than for usual printed boards and the like.